Effective processing of data having complex relationships is an everlasting task of the computer science. For instance, one of typical tasks in this field is migrating objects from one or more computer applications or databases to a single target computer application or database, e.g. in the context of a consolidation or harmonization project, wherein a number of existing systems are replaced by a new system. This also includes incorporating additional source systems comprising the objects into an already existing target. This problem gets further complicated, when the objects comprise instances linked by relationships. Thus migrating of the objects from one computer application to another requires not only transfer of the instances but transfer and update of their relationships.